


Until Death Do Us Part

by MageOfLight



Series: i swear, this was supposed to just be poly skeleheat sin. now there's an extended story. huh. [7]
Category: Undertale
Genre: Ecto-Genitalia, HoneyCherryBerry, M/M, Monster Marriage, basically i felt like writing happy fluff followed by sin, because i've not seen any fics like this so i have no one else's headcanons to consider, haha - Freeform, light rope bondage, prepare for headcanons i'm making up on the spot, set in Underswap so all the characters except Red are Underswap natives, so enjoy i guess?, soul bonding
Language: English
Status: Completed
Published: 2016-11-16
Updated: 2016-11-16
Packaged: 2018-08-31 09:20:20
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,872
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8572876
Author URL: https://archiveofourown.org/users/MageOfLight/pseuds/MageOfLight
Summary: Papy, Red, and Blueberry get married! Everyone is super happy for them.Set 6 years after UF!Sans' arrival in Underswap.





	

**Author's Note:**

> technically, this should be the end of the series? but i got a sudden burst of inspiration while half dead with exhaustion. this is the results of that. lmao
> 
> notes regarding headcanons are at the end for spoiler reasons.

The ceremony was a small, private affair, everyone dressed their best in celebration of an imminent soul bond, with Queen Toriel and King Asgore presiding over the whole thing. It was, of course, a rather unusual set up, what with brothers and their 'cousin' being the ones getting married, not to mention the fact that it was three monsters in general, but unlike humans, monsters didn't really share the same taboo on incest. Simply put, everyone was extremely happy to see them finally tying the knot after several years of courtship between the three of them.  
  
"If anyone has anything to say about the bonding of these three monsters, speak your piece now," Asgore called. Silence filled the room, not even the few humans that had been invited had anything to say, much to everyone's relief. No one had been sure how they would take knowing their monster friends were quiet a bit more different in their customs than humans thought.  
  
"Then, bring the rings forward," Toriel uttered solemnly. Chara was unable to help the sunny smile that stretched their face as they stepped forward to the half circle their friends had formed, opening the glass box that held the rings. They were special, bands of magic-laced metal that would aid in the more private part of the soul bonding later (and that had been an... interesting talk for the 18-year-old royal child). Chara schooled their face as best as they could, attempting to take on the more formal air they were supposed to be carrying for their part of the ceremony, but it was honestly no use. They were just too happy for their three friends. They did manage to temper their wide grin into a much smaller smile, though. It would have to do.  
  
Carefully, they lifted the first ring from the box. They weren't really rings in the same sense as a human wedding ring, of course. They were more like cuffs, a wide band of thin, decorative metal that wrapped around a monster's wrist and bound them to their bondmate in preparation for their soul bond later. Chara gently clicked the first ring around Papyrus' right wrist. The second went on Red's left, and a visible chain of pure magic, unbreakable, yet intangible linked them. The third and fourth went on Red's right and Blue's left, and the fifth and sixth went on Blue's right and Papyrus' left, completing the circle. Chara then stepped back from the circle with their empty box, a small worried frown replacing their smile. All three of them looked kind of unsteady. The magic linking them was their own, though, so it was no surprise. They had to have been feeling the drain from that. But they looked happy, despite the sweat beading on their faces, so Chara shook off their worry and stepped back to their place in the wedding party, clutching the ring box to their chest. It would go with the trio when they left later, but for now, it was still their job to carry it.  
  
The King and Queen both stepped forward then, hovering their hands over the three skeletons. A flair of fire magic from each of their hands burst out and touched the rings, sealing them. They would be completely unremoveable until the bond was completed. However, with that, the ceremony was completed. The trio suddenly found themselves wrapped up in massive, furry hugs. "Good luck to you three. You've chosen a bit of a difficult path," Toriel whispered. While it wasn't completely unheard of for three or more monsters to bond, it was very rare for it to happen because of the strain it put on the souls of the monsters. Even then, they'd usually decide to bond one pair at a time, rather than all at once. The skeletons knew they'd picked the hardest way, but they were all positive they could handle it, too.  
  
As soon as the king and queen stepped away, the trio were swept up in the festivities of the bond party. Gifts were given, a dinner of traditional foods meant to bolster the magic of the future bondmates was had, leaving most of the guests jittery with excess energy (hilariously enough, it was the humans that were most effected by the food, the younger ones practically bouncing off the walls), followed by a massive cake being cut and spread out among the guests. The cake wasn't something normal for a monster wedding, but their human friends had suggested it, and the monsters thought it was a good idea. After that was another three hours of partying before Papyrus, Red, and Blue could officially excuse themselves, flushed faced and eager to return home.

\--------------------------------------------

"fuck, I thought they'd never let us leave," Papyrus groaned, shutting the front door behind him. He swore Toriel and Asgore had been purposely foiling their attempts to leave earlier. Now it was all he could do to keep from pouncing his two smaller lovers. Sighing, he turned around only to gulp somewhat loudly and bite back a growl as he saw Red and Blue were already kissing, tongues tangling between their mouths. Both their pelvises were bright with magic, faintly visible even through the thick robes they had to wear for the ceremony.  
  
"heh, i know... it was getting kinda painful," Red replied, breaking the kiss to aim a half-lidded stare at Papyrus, smirking devilishly at him. "but we're home now, so what say we get upstairs?" he winked, and Papyrus groaned, letting each of his hands be grabbed by the smaller pair.  
  
Before they could start dragging him up, he smirked and pulled them both through a shortcut that conveniently dropped the smaller pair on the bed of his bedroom and left him standing at the foot, still holding both their hands. Both of them laughed somewhat breathlessly before Red reached up and pulled Papyrus down for a kiss. He fumbled for a moment with the fastenings of Papyrus' robes, before drawing away from the kiss with a triumphant sound as the robes fell away, leaving him utterly naked, the glow of his soul and the magic gathered at his pelvis lighting up the room in a soft, orange glow. "shit, yer so gorgeous, pap..." Red murmured, hand coming to rest over the taller's sternum reverently.  
  
Blue looked up from putting the box on the floor next to the bed and let out a quiet, pleased hum at seeing Papyrus naked, but then smiled brightly, moving to sit behind Red. Papyrus watched a moment as Blue reached for the fastenings of Red's robes, then leaned forward to reach for Blue's, sandwiching Red between them. Red didn't appear to mind too much, as he let out his own little hum, licking at Papyrus' chest, drawing a moan from him. Soon enough, all three of them were naked, except for a crimson rope tied around Red's leg and tail, Papyrus having bound the wild appendage before the ceremony. He took a moment to make sure the rope was still in place correctly, then let himself be pulled up into a kiss by Blue.  
  
While the two of them kissed, Red wasn't idle, dropping slightly to lick at Papyrus' unformed magic. Papyrus moaned into Blue's mouth at the feeling, letting his magic coalesce into a thick cock, knowing Red really liked sucking. Well, not that he didn't have the same oral fixation, if he were to be honest. Red went to work immediately, drawing Papyrus' dick into his mouth, his tongue coiling in that clever way that drove Papyrus to twitch his hips forward into Red's mouth. Red moaned as Papyrus pushed into his already formed throat and he keened at the feeling, pulling away from kissing Blue with a gasp. "stars, Red," Papyrus hissed, petting Red's skull. The bugger had the gall to start purring at the gentle touch, sending maddening vibrations through Papyrus' magic. "shit, keep that up and I'm gonna cum..." Red looked up and _winked_ , making Papyrus groan before pulling back out of Red's mouth, though it wasn't without a disappointed sound from both of them. Blue quickly took Papyrus' place, thrusting his length into Red's open mouth and earning a happy little sound from the fanged skeleton that, quite frankly, was a little too adorable for the situation.  
  
Papyrus shook his head at that, then bent forward to return the favour. Red had, over time, taken a liking to forming both masculine and feminine parts, something Papyrus sincerely enjoyed as well. Grinning, he licked and nibbled lightly at Red's cock, trailing his fingers along the outside of the entrance just below. Red cried out at the feeling, jerking his head off Blue to avoid biting him by accident. "f-fuck, papyrus..." Red groaned.  
  
"Oh, wow, Papy... that made his soul glow brighter," Blue commented with an awed sound. Papyrus looked up, noting with interest that the faint light that had been shining from inside Red's ribcage was, indeed, a lot brighter than it had been. Blue's soul, when he looked, was brightening in response, and he had no doubt his own was likely doing the same. The magic that linked their rings was also starting to glow brighter, and he hummed softly.  
  
"I guess it's time to get this show on the road then," Papyrus commented, smiling as he stood up. The smaller skeletons nodded and started shuffling back on the bed, giving the taller room to join them. They wanted to be comfortable for this. "Blue, change up your equipment there. you probably won't be able to focus enough to do it in a minute," Papyrus ordered, and Blue flushed.  
  
"Yes, Papy," Blue replied, obediently doing what Papyrus told him. His magic warped and shifted until he had a cunt, already wet with arousal. Red leaned in without prompt, lapping at it until Blue was crying out and thrusting his hips up at Red's face in an attempt to get more. Papyrus pulled Red away, though, kissing him for a moment before grinning.  
  
"are we all ready?" the taller asked. Red and Blue nodded again, then all three of them let their souls coalesce properly, hovering in front of their chests. The normally white inverted hearts were all flushed with magic, shining their respective colours and oozing slightly, looking kind of like they were attempting to melt. With their souls out now, Papyrus gently guided Red, nudging him up Blue's body. Red took the hint, settling between the slightly smaller skeleton's legs and leaned forward, kissing his sternum. Blue moaned as he felt Red's cock brush his cunt, then moaned again, louder, as Red adjusted himself to push against the opening without actually penetrating him. Yet, anyway. Once Red was all lined up, Papyrus leaned over them both, pressing against Red's opening, causing Red to groan lowly in response. If any of them were to glance up, they'd see their souls gravitating toward each other, moments away from touching.  
  
"Please... Red, Papy..." Blue moaned, reaching up for both of them. One hand curled around the back of Red's bare neck, the other caught in Papyrus' ribs, hooking around them and tugging lightly.  
  
"ah, fuck, are ya really gonna make us both beg, pap?" Red asked. Papyrus huffed an amused laugh, but rather than responding verbally, he just grinned and thrust forward, hilting himself and at the same time, forcing Red to push into Blue, hilting as well. Both smaller skeletons cried out loudly at the sensation.  
  
"fuck, Sans..." Papyrus groaned and both of them moaned at hearing their real name after such an extended period of just being called by their nicknames. Papyrus twitched his hips at the sounds they were making, but before he could do much more than that, their souls made contact above them. The world seemed to blank out replaced by nothing but pure, overwhelming sensation. He could feel _everything_ his partners were feeling, every emotion, every physical sensation. They flooded through him in a wave, and all he could do was gasp and hold on.  
  
When the rest of the world filtered in again, he found himself thrusting hard into Red, who'd apparently found a rhythm to follow between him and Blue. He also found something was wrapped rather securely around his spine and tangled in his ribs. That something happened to be Red's tail, when he focused himself enough to look without slowing his thrusting. He didn't know how much time had passed, exactly, though all three of them must have cum at least twice. The bed was a mess, Red had translucent release, both his own and Papyrus' dripping down his legs, and Blue was babbling nonsense, something that only happened when he was completely wrecked. He didn't have a chance to make anymore observations, though, as suddenly, Red's hips stuttered and stopped, buried deep in Blue. Papyrus could feel Red's walls flutter and clamp around him as the smaller came, and he groaned.  
  
"shit, Red... you're so tight," he hissed, thrusting in a couple more times before he felt himself falling over the edge as well, stilling inside and letting himself cum before nearly collapsing, exhausted, on top of Red. It was only by shear chance he was able to get his arms out in time to catch himself from flattening both Red and Blue, though when he tried to pull back, he was halted by Red's tail. He couldn't even pull out. All he could do was carefully pull Red with him before tilting to the side, Red moaning weakly as the movement caused Papyrus' cock to shift inside him. Like that, all three of them passed out, needing the rest.

\--------------------------------------------

Red came to with a soft groan, shifting minutely only to gasp and moan at a rather startling feeling. There was a cock inside his still formed magic, and the owner of said cock was rocking back and forth in short movements that sent little bolts of pleasure shooting up his spine. Opening his eyes, he met Blue's sleepy, yet insanely interested gaze. The others eyelights were not on his face, though. They were instead firmly locked on his pelvis. He looked down himself, finding that at some point, his magic had shifted to be settled completely on a pussy, the semi-translucent magic showing Papyrus' cock moving in short, lazy thrusts. "shit..." he muttered, looking back over at Blue, who was stroking himself. An idea suddenly entered his head, and he flushed, groaning at the thought. Still, he wanted to try it. "hey, Blue. wanna try something?" he asked, grinning, then gasping as Papyrus thrust a little harder. His movements were still maddeningly shallow, though, and he twitched, looking over his shoulder to discover Papyrus's eyes closed, his mouth open slightly, a faint trail of drool escaping to soak into his pillow. He could have laughed. Papyrus was fucking him in his sleep.  
  
"What is it?" Blue asked, voice quiet, but curious. He was clearly aware that Papyrus was still sleeping, and perhaps intended on letting him stay that way. Well, Red certainly hoped that wouldn't be the case. He wanted Papyrus to really start moving. He couldn't cum like this. Though... with what he had in mind, perhaps he'd be able to, even with Papyrus asleep.  
  
"i want ya ta fuck me," he told Blue, then held up a hand as Blue opened his mouth, looking ready to protest. "yes, i'm more than aware pap is already in there. i want ya, too, though. stretch me out first," he whispered, grinning as Blue let out a whine, his expression telling Red he was becoming far more interested in the idea.  
  
"L-let me know if it hurts, okay?" Blue murmured. Red nodded, then gasped as Blue slipped two phalanges inside him, forcing him a little wider. It didn't take long before an astonished looking Blue was sliding in a third, then a forth, stretching Red out. All Red could do was moan and writhe, doing his best to thrust against Papyrus' cock and Blue's fingers, though it felt like something was holding him back from the movements.  
  
"stars, blue, that's enough. please, fuck me," Red gasped, twitching. Blue thrust his fingers in a few more times before giving a satisfied look and moving in until he could press the head of his cock against Red's opening. Red hooked a leg over Blue's hip, using it and his hands to pull Blue in closer. He felt a bit of a stretch and a mild burn as he was breached by Blue's cock. For some reason, he felt like it should have actually hurt, but after a moment, all he could feel was an immensely satisfying stretch as Blue hilted himself. Papyrus keening softly behind him just added to the building pleasure. "i'm okay. move," Red said, tone nearly begging as Blue opened his mouth. The other's jaw snapped shut, face twisting to a determined expression as he did what Red wanted. He started with a gentle rock, moving counterpart to Papyrus, but that didn't last long. Soon enough, he was thrusting hard and fast, pulling out almost completely before ramming back in. Red was quickly reduced to a moaning, screaming mess, which naturally woke Papyrus up.  
  
"...holy shit..." Papyrus groaned, though Red didn't really hear him, too busy losing his mind from the sensation of being fucked like he was. All he could do was cling to Blue, unknowingly tightening his tail around Papyrus, causing him to moan as it rubbed and squeezed several sensitive places at once. Papyrus, now conscious of what he was doing, shifted, thrusting harder and faster into Red, who keened loudly in response, his walls tightening around both cocks until neither could do more than rock shallowly into him, drawing out his orgasm and tipping both of them over the edge in the process.  
  
When the three of them came down, Blue carefully pulled out, though Red still hissed at the drag against his overly sensitive magic. "nn, stars, that was good..." Red murmured, pulling Blue back for a kiss. Blue complied, humming happily into it before moving away to kiss Papyrus over his shoulder, only to stop and laugh.  
  
"Well, that certainly explains a lot!" he nearly chirped, grinning.  
  
"uh... what?" Red asked, looking puzzled, only to gasp and whine as Blue reached over and stroked the base of his tail. The touch felt like it was on more than just the base, though, and as Red squirmed, keening as Papyrus' dick shifted inside him (why hadn't he pulled out yet???), Papyrus laughed breathlessly.  
  
"nn, fuck... your tail's been wrapped around me since before we passed out last night. Probably broke the rope when the bonding started," Papyrus told him, and Red managed to look back over his shoulder again, pure shock driving him. Sure enough, his tail was looped around and through Papyrus' bones. Well, that explained why Papyrus wasn't pulling out... Through sheer willpower alone, despite the exhaustion starting to drag him down, Red managed to loosen his tail, allowing Blue and Papyrus to gently drag the appendage away from Papyrus until it was laying limply on the bed behind him, partly pinned under the taller, who took the chance to pull out of Red finally.  
  
Red whined softly at the feeling of being completely empty after who knew how long of having Papyrus inside him, but he bit back the urge to ask one of them to fill him again, letting his magic finally dissipate as he rolled partly onto his back, looking up at their souls above them. The three souls had combined as part of the bonding and they were still joined, the single combined soul above them flowing with all three of their magic colours, mixing and blending. It was beautiful, but they were extremely vulnerable like this.  
  
"...I guess it's about time for the hard part, huh?" Blue asked quietly, and Red looked over to find his counterpart's eyelights fixed on the inverted heart. When he looked to his other side, Papyrus was also staring up on it. Both of them had looks of awe on their faces that must have been a reflection of his own expression when looking at their combined souls. Blue was right, though. They couldn't stay like this forever, as nice as it was feeling the two of them so _close_. He was also right in that this was the hard part. They'd been joined for hours already, which was likely going to make this harder. They needed to separate.  
  
Almost as one, they all sluggishly sat up, moving to sit in a circle, bracing each other with gentle hands. They all nodded and closed their sockets, focusing. Red furrowed his browridges at the first sensation of pulling. It started gentle, but it slowly got more intense the longer he kept it up. It was hard to think only of himself, carefully pushing at his bondmates until finally, finally, he'd pulled free. Time seemed to slip as a sense of muted agony washed over him, feeling more drained than he had in a long, long time. He was too tired to really feel the pain, but his body still spasmed, and vaguely, he felt the same from Papyrus and Blue. Worry for his bondmates tried to sweep over the bone-deep exhaustion, but he couldn't fight it enough to open his eyes and check on them. The vague awareness he was clinging desperately to slipped, and he passed out, not even feeling as the rings snapped open and fell off his wrists.

\--------------------------------------------

Awareness filtered back in along with a dull, body consuming ache and Blue whimpered. Stars, how he didn't want to be awake at that moment. It felt like he'd gone on a marathon training session with Alphys. However, when memory of the reason for his pain filtered in Blue snapped awake completely, forcing his eyes to open. He was laying in a tangled heap with Red and Papy, both of whom were breathing raggedly. Blue couldn't imagine their positions helped much with that, laying in limp heaps as they were. Hissing, Blue carefully pulled himself from the pile and looked up. Their souls were still there, back to their normal white with the exception of two delicate rings of coloured magic coiled around each one, forever marking them as belonging to and with each other. The sight caused Blue to feel considerably lighter, the ache not bothering him nearly as much. It was worth it. They'd succeeded in their three-way bond and come out the other side okay, their souls undamaged, for all he felt like death warmed over at the moment.  
  
With a happy little sigh, Blue set about getting his unconscious mates into more comfortable positions, carefully pulling them up to lay in bed properly and covering them with the blankets (which, he noted with dismay, were utterly ruined. There'd be no getting the magic stains out now), before moving the rings off the bed, setting them on top of their box. He then moved back to settle in with his mates, staring happily up at the trio of souls. He couldn't wait until Red and Papy came around and got a look.

**Author's Note:**

> the three of them then spend the next two weeks holed up in bed, existing on precooked food and snacks. monster honeymoons consist of recovery time because the process of bonding, while fun, puts a lot of stress on the monsters. blue was going stircrazy by the end of the first week.
> 
> okay, so just for clarification, the way soul bonding goes for this is that most monsters go for permission from royalty to bond. the king/queen grant the monsters their blessing, then a ceremony is held.
> 
> the reason for this is soul bonding can be dangerous. extremely so. if one monster is more powerful than the other, the weaker monster can be overwhelmed by the stronger if they aren't being careful, and depending on the difference, the weaker could wind up dying. The rings that monsters are given during the ceremony force the future bondmates' magic to sync up and balance, so that the threat of one partner overwhelming the other is no longer an issue. This also has a side effect of the monsters' souls manifesting, which is part of the reason for the thick robes. They are protection against anyone that may try and attack the monsters while they are vulnerable. The robes and rings are returned to the king and queen once the bond is completed and the new bondmates have recovered from their bonding.
> 
> if you have any questions that weren't answered, feel free to ask. :)
> 
>  
> 
>  **EDIT 12/4/2016:** gosh, guys, i know you feel bad for Underfell Papyrus, but seriously. i had Big Reasons for stating that _Meanwhile, In Underfell..._ is the only _canon to this series_ entry that will include him. here are those reasons;  
>  1: even if Red wanted to go back to finally close that door to his past, he wouldn't have the courage to go back alone, and he would absolutely refuse to put his bondmates in danger. and yes, as far as he is aware, going back WOULD be dangerous.
> 
> 2: he has absolutely no hope for his brother or his universe. as far as he is aware, Edge will never go back to being the sweet little skeleton he was when he was a kid, and the underground will remain violent and loveless. even if the barrier is one day broken, the monsters will start a war and be utterly massacred by the humans fighting to protect themselves. he IS right in that Edge will never return to that innocence, but he has no clue about Frisk, monster tamer extraordinaire, and thus has no clue that anyone could talk some sense into his brother.
> 
> 3: neither him, nor Papy are aware of the fact that the Machine is not just a time machine. as far as they are aware, Gaster was building a time machine in order to go back and stop the war before it even began. they aren't even sure how Red got to the swapverse in the first place. Red thinks it was a combination of backfired time magic generated by his Machine and a bad shortcut. it's the only explanation they have that makes even a lick of sense to them.
> 
> 4: if i did manage to think of some way to get Red back to Underfell, it would be via an accident, and he would be alone, separated from his bondmates with no idea how to get back. even having his brother there to support him wouldn't be enough to keep him from pining for his partners until he falls. so yeah, if you're looking for a majorly heartbreaking ending to this 'verse... i could always do that. because as my writing buddy knows, i'm seriously not above seriously hurting my babies. ::cackles evilly:: (...unless it's doing a genocide route. i can't. i cannot do it. i cannot harm goatmom or the skelebros in game. i just seriously cannot do it. my frisk is a hard core pacifist.)
> 
> i'm not changing my mind on any of this no matter how much you guys beg me, so please stop asking. if you want to see some fluff for the brothers, there is a non-canon piece where Red and his bondmates go visit Underfell. it isn't linked to the series, but it's not hard to find, either.

**Works inspired by this one:**

  * [This Is Not Canon, But Here, Have Some UFbro Fluff](https://archiveofourown.org/works/8553106) by [MageOfLight](https://archiveofourown.org/users/MageOfLight/pseuds/MageOfLight)




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